1. Field of the Invention
The present invention relates generally to a medical instrument, and, in particular, to a device for implanting spiral cuff electrodes about the trunk of a nerve for the introduction of electrical signals.
2. Description of the Related Art
The use of electrodes to stimulate nerves and other body tissues has been well known for many years. More specifically, the use of nerve cuff electrodes, which are self-biased to wrap around a nerve trunk in a spiral to provide close contact, has become an accepted method for nerve stimulation, as the structure of the electrode allows it to be installed around the nerve fiber without cutting or damaging the nerve. Another advantage of spiral nerve cuff electrodes lies in the fact that these electrodes require less stimulating current than other types of electrodes, and hence less charge injected into the tissue. In addition, cuff electrodes allow easy excitation of entire muscles rather than parts of muscles.
Various prior art cuff electrodes have been utilized in the past to apply electrical stimuli to nerves. U.S. Pat. No. 4,602,624 is directed to a cuff electrode which encircles a nerve trunk with at least one electrical energy conductive member held against the tissue and a non-conductive sleeve extending to either side of the conductive member. This cuff is a self-curling sheet which is biased to curl into a tight overlapping cylindrical spiral around the nerve trunk. U.S. Pat. No. 5,324,322 is directed to a nerve cuff electrode having a spiral cuff portion which is connected to a spiral lead portion. The spiral cuff portion is coiled around a nerve, while the spiral lead portion used to couple the device to an appropriate power source. U.S. Pat. No. 5,505,201 is directed to a helical nerve cuff electrode which curls into a helical spiral around a nerve fiber as it is ejected from a carrier tool.
Although these spiral cuff electrodes have proven effective, they do have drawbacks. As these electrodes are very delicate in construction, with very small and fragile wires and connections, the installation of cuff electrodes requires a very sensitive and exacting surgery. When these electrodes are to be installed in hard-to-reach areas of the body, it is often very difficult to implant them satisfactorily. The instrument used to install these electrodes must be rigid in construction to be able to carry and place the electrodes, yet flexible in order to maneuver the electrodes into the proper position in minimally accessible areas. In addition, the tool must be able to maintain the electrode in a flat uncurled position until ready for implantation, while it may be necessary to control the implantation of the electrode from a position remote from the implantation site.
The present invention provides a novel tool for implanting spiral nerve cuff electrodes which overcomes the above referenced problems and provides other advantages for the procedure.